U.S. patent number 10,556,289 [Application Number 14/535,917] was granted by the patent office on 2020-02-11 for welding type power supply for tig starts.
This patent grant is currently assigned to Illinois Tool Works Inc.. The grantee listed for this patent is Illinois Tool Works Inc.. Invention is credited to Andrew D. Nelson, Quinn W. Schartner, Bernard J. Vogel.
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United States Patent |
10,556,289 |
Schartner , et al. |
February 11, 2020 |
Welding type power supply for TIG starts
Abstract
A method and apparatus for TIG welding and starting a TIG
welding process includes limiting the pulse width of a power
circuit when a TIG start is being performed, and monitoring for the
creation of a welding arc. After the welding arc has been detected
the limiting of the pulse width is ended.
Inventors: |
Schartner; Quinn W. (Kaukauna,
WI), Vogel; Bernard J. (Troy, OH), Nelson; Andrew D.
(Grand Chute, WI) |
Applicant: |
Name |
City |
State |
Country |
Type |
Illinois Tool Works Inc. |
Glenview |
IL |
US |
|
|
Assignee: |
Illinois Tool Works Inc.
(Glenview, IL)
|
Family
ID: |
54325745 |
Appl.
No.: |
14/535,917 |
Filed: |
November 7, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20160129514 A1 |
May 12, 2016 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23K
9/09 (20130101); B23K 9/092 (20130101); B23K
9/1031 (20130101); B23K 9/167 (20130101); B23K
9/067 (20130101); B23K 9/0677 (20130101) |
Current International
Class: |
B23K
9/067 (20060101); B23K 9/09 (20060101); B23K
9/10 (20060101) |
Field of
Search: |
;219/130,131,132,135 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
International Search Report, dated Feb. 9, 2016, European Patent
Office, Rijswijk, Netherlands. cited by applicant.
|
Primary Examiner: Hoang; Tu B
Assistant Examiner: Ward; Thomas J
Attorney, Agent or Firm: Corrigan; George R.
Claims
The invention claimed is:
1. A method of starting a TIG welding process, comprising: limiting
the pulse width of a power circuit to be less than a desired
magnitude when a TIG start is being performed; monitoring for the
creation of a welding arc; and ending limiting the pulse width
after the welding arc has been detected.
2. The method of claim 1, further comprising delaying ending
limiting the pulse width after the welding arc has been
detected.
3. The method of claim 1, further comprising delaying ending
limiting the pulse width after the welding arc has been detected
for a fixed period of time.
4. The method of claim 1, further comprising delaying ending
limiting the pulse width after the welding arc has been detected
for at least one millisecond.
5. The method of claim 2, further comprising providing a closed
loop control after ending limiting of the pulse width.
6. The method of claim 5, wherein limiting the pulse width includes
providing an output voltage of about 10 volts.
7. The method of claim 6, wherein limiting the pulse width of a
power circuit is done when a TIG scratch start is being
performed.
8. The method of claim 1, wherein monitoring includes monitoring
the output voltage.
9. The method of claim 1, wherein monitoring includes monitoring
the output current.
Description
FIELD OF THE INVENTION
The present disclosure relates generally to the art of welding type
power supplies. More specifically, it relates to starting a TIG
process using a welding type power supply.
BACKGROUND OF THE INVENTION
There are many different welding processes. One welding process is
a TIG process. Tungsten inert gas (TIG) welding is an arc welding
process that uses a non-consumable tungsten electrode to produce
the weld. The weld area is protected from atmospheric contamination
by an inert shielding gas (argon or helium), and a filler metal is
typically used. TIG welding is usually performed using CC (current
controlled) power. Welding type power supply, as used herein, is a
power supply that provides welding type power. Welding type power,
as used herein, is power suitable for welding, induction heating,
or plasma cutting.
There are many different topologies used in welding type power
supplies. Switched power supplies are often used to allow for
output control. One prior art welding type power supply includes a
preregulator, a high voltage split bus, and a stacked inverter
output, and is shown in patent application Ser. No. 13/839,235,
published as US-2014-0021180-A1, hereby incorporated by reference.
This power supply is well suited for controlling the output using
pulse width modulation of the output inverters. Another prior art
welding type power supply well suited for pwm control of the output
is described in U.S. Pat. No. 8,455,794, also incorporated by
reference.
Starting a TIG weld can require skill. Typical methods of starting
a TIG process include using HF, lift art, and scratch start. Lift
starts require specific controls, and the user touches the arc to
the workpiece. As the electrode is lifted the arc is struck. HF
starts are easy and reliable, but can cause interference with other
equipment and requires the machine have the capability of providing
an HF output. Scratch start requires no extra equipment, but
requires the most skill. Scratch start involves sweeping the
tungsten across the work piece.
TIG starts can "stick" and leave tungsten on the workpiece. This is
particularly a problem for non-HF starts, and most particularly a
problem for scratch starts. One cause of sticking is current
overshoot during arc initiation. Current overshoot can happen
because the power supply has a fast output current slew rate (this
may be desirable at times other than the start and for other
processes). Accordingly, a welding type power supply that provides
reliable starts for TIG welding, while not sacrificing a fast slew
rate after starting, is desired.
SUMMARY OF THE PRESENT INVENTION
According to a first aspect of the disclosure a method of starting
a TIG welding process includes limiting the pulse width of a power
circuit when a TIG start is being performed, and monitoring for the
creation of a welding arc. After the welding arc has been detected
the limiting of the pulse width is ended.
According to a second aspect of the disclosure a welding type power
supply includes a switched power circuit and a controller. The
switched power circuit receives input power and provides welding
type power to a welding output. The power circuit has a control
input. The a controller includes a control output connected to the
control input, and a feedback input that receives feedback
indicative of the presence or absence of an arc. A pwm module is
connected to the control output, and a pulse width limiting module
is connected to limit the pwm module. The pwm module is responsive
to the feedback input.
The ending of the limiting of the pulse width is delayed after the
welding arc has been detected, in one alternative.
The delay to end the limiting of the pulse width is a fixed period
of time, in another alternative.
The delay to end the limiting of the pulse width is one millisecond
in one embodiment.
Closed loop control of the output is provided after the limiting of
the pulse width has ended, in various embodiments.
Limiting the pulse width includes providing an output voltage of
about 10 volts, in one alternative.
The TIG process is started using a scratch start in another
alternative.
A feedback circuit is connected to the welding output and connected
to the feedback input in one embodiment.
A delay module is included and the pulse width limiting module is
responsive to the delay module in various embodiments.
The delay module is responsive to the feedback input, in one
alternative.
The delay module is a fixed time delay module in another
alternative.
The delay module is a one millisecond delay module. in one
embodiment.
Other principal features and advantages of will become apparent to
those skilled in the art upon review of the following drawings, the
detailed description and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a welding type power supply; and
FIG. 2 is a block diagram of the controller for the welding type
power supply of FIG. 1.
Before explaining at least one embodiment in detail it is to be
understood that the invention is not limited in its application to
the details of construction and the arrangement of the components
set forth in the following description or illustrated in the
drawings. The invention is capable of other embodiments or of being
practiced or carried out in various ways. Also, it is to be
understood that the phraseology and terminology employed herein is
for the purpose of description and should not be regarded as
limiting. Like reference numerals are used to indicate like
components.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
While the present disclosure will be illustrated with reference to
particular welding type power circuits, controllers, modules and
components, it should be understood at the outset that the
invention can also be implemented with other welding type power
circuits, controllers, modules and components.
Generally, the present invention provides for using PWM control of
the output of a welding type power supply to provide a desirable
start for TIG welding. A welding type power supply 100 (FIG. 1)
includes, in the preferred embodiment, a power circuit 102 and a
controller 104. The output of power circuit 104 is a welding arc
106. Power supply 100 may be a multi-process welding type power
supply, but the present invention will be explained with reference
to a TIG mode of operation.
Controller 104 is preferably a digital pulse width controller, such
as that described in U.S. Pat. No. 8,455,794. Controller 104 may
also be such as that described in US-2014-0021180-A1. Alternatives
provide for an analog controller, a digital controller with
discrete elements, a controller using DSPs, and a controller using
other circuitry.
Power circuit 102 is preferably the power circuit shown in
US-2014-0021180-A1, which includes a preregulator, a high voltage
split bus, and, as an output converter, a stacked full bridge
inverter output circuit. It may also be implemented using the power
circuit shown in U.S. Pat. No. 8,455,794. Alternatives provide for
using the output circuit (stacked inverters) without the
preregulator, a half bridge output converter, or other output
converters, such as a chopper, buck, etc., and using intermediates
stages.
Feedback is provided from power circuit 102 on lines 111, and from
the output on lines 107 and 108. The feedback may be indicative of
the bus parameters (current, voltage, ripple, etc.), and may be
indicative of the output parameters (current, voltage, power
polarity, etc.), and may be indicative of the presence or absence
of the arc (for example sensing current or voltage). Control
signals are received by power circuit 102 on lines 110. The control
signals received on 110 control the switching of switches in power
circuit 102, including preregulator and output converter
switches.
Controller 104, shown in FIG. 2, includes a PWM module 201 that
receives feedback of the output of power circuit 102 (or feedback
from within power circuit 102). In response to this feedback
controller 104 and PWM module 201 pulse width modulates switches in
power circuit 102 so that the output is a desired output. PWM
module, as used herein is a module that controls the pulse width of
a power circuit, so as to provide a desired output. Module, as used
herein includes software and hardware that cooperate to perform a
given function.
When the user selects the TIG mode of operation (or if it is a
dedicated TIG machine), controller 104 and PWM module 201 cause the
output of welding type power supply 10 to be a cc (current
controlled) output at a user setpoint. Also, when the TIG process
is initiated the preferred embodiment limits current overshoot to
reduce the likelihood of tungsten electrode sticking during arc
initiation. The invention limits current overshoot by limiting the
slew rate, and specifically, limits the pulse width to enable
better control of the output current slew rate during arc
initiation. Preferably the duty cycle is limited to a pulse width
that results in about 10V or less under load until an arc voltage
is detected (meaning the start is over). One embodiment delays
closed loop control for 1 ms after the arc is detected, to insure
the arc is stable before ending the limited pulse width. The arc
can be detected by monitoring output voltage, current, or both an
comparing the detected parameter to a threshold or value.
Alternatives use a longer or shorter delay than 1 msec.
Controller 104 provides for the desirable TIG start using a pulse
width limiting module 203, which limits the pulse width to slow the
slew rate of the output, and the output is less than that which
would be provided but for module 203. This makes sticking during a
TIG start less likely. Pulse width limiting module 203 limits the
output to about 10 volts, in the preferred embodiment. About 10
volts, as used herein, is an average of 8-12 volts. Pulse width
limiting module, as used herein, is a module that controls the
pulse width of a power circuit, so as to limit the pulse width to
be less than the pulse width that would be provide absent the pulse
width limiting module (i.e., less than the pulse width called for
by the normal control).
Pulse width limiting module 203 receives feedback signals on inputs
107 and 108 that are indicative of the presence or absence of the
arc (if current is used, then only one feedback line could be
used). At start up (when current is drawn, e.g.) pulse width
limiting module 203 is activated, limiting the pulse width set by
pwm module 201. Then, when the feedback signals 107/108 indicate
the arc is established, pulse width limiting module 203 is
deactivated, in one embodiment. The preferred embodiment uses a
voltage threshold to determine when the arc is present. For
example, a voltage of less than 10 volts could be used to indicate
the arc has not been established. Other threshold may be used.
Various alternatives provide for using current, voltage, or a
combination thereof to determine when an arc is established.
In another embodiment a delay module 205 also receives feedback
signals 107/108, and delays the deactivation of pulse width
limiting module 203. Delay module 205 can also be connected to pwm
module 201. Delay module, as used herein, is a module that causes a
delay from the time an event is sensed, to the time when there is a
change in a command. Delay module 205 is a fixed time delay module
in one embodiment. Fixed time delay module, as used herein is a
module that causes a delay of a fixed time from a sensed event to a
change in a command. Delay module 205 is a one millisecond delay
module, in another embodiment. One millisecond delay module, as
used herein, is a module that causes a delay of one millisecond
from a sensed event to a change in a command.
The preferred embodiment provides that the control modules are
implemented in software using a digital pwm controller such as that
in U.S. Pat. No. 8,455,794. Alternatives provide for hardware to
implement the control modules. The preferred embodiment provides
that the TIG start is done using a scratch start, although it may
be done with lift and HF starts.
Numerous modifications may be made to the present disclosure which
still fall within the intended scope hereof. Thus, it should be
apparent that there has been provided a method and apparatus for
providing welding type power for starting a TIG process and for
welding that fully satisfies the objectives and advantages set
forth above. Although the disclosure has been described specific
embodiments thereof, it is evident that many alternatives,
modifications and variations will be apparent to those skilled in
the art. Accordingly, the invention is intended to embrace all such
alternatives, modifications and variations that fall within the
spirit and broad scope of the appended claims.
* * * * *